Among the compositions that are currently used to carry anti-tumor compounds to tumor cells, acting as a site-specific anti-tumor drug, are compositions of nitrogen mustard and various steroid hormones, typified by the compound of normustine and oestradiol. Such compounds utilize the concept of steroid hormones such as estrogen as a carrier of the inert cytotoxic agent directed to the target tissue where cleavage of the molecule by hydrolysis releases active normustine. With many compounds of this type, the use thereof is accompanied by such undesirable side effects as hormonal side-effects, emetic properties, and mood-depression which augment that depression which frequently accompanies traumatic illness such as cancer.
There is, accordingly, a present need for therapeutic agents utilizing the concept of a carrier and an inert cytotoxic agent which can be carried to the target tissue where cleavage of the molecule will release the cytotoxic agent, without the undesirable side effects heretofore associated with many of the presently used compositions.